Question

If a ripe apple is kept in a basket with unripe apples it causes the ripening of all the unripe ones . How?

Answer 1

As they ripen, some fruits, like apples and pears, produce a gaseous hormone called ethylene, which is, among other things, a ripening agent. When you store fruits together, the ethylene each piece emits prods the others around it to ripen further, and vice versa.

The riper a piece of fruit is, the more ethylene it produces, and overripe fruit gives off even more ethylene, eventually leading to a concentration of the gas that’s enough to overripen all the fruit. Given the right conditions and enough time, one apple can push all the fruit around it to ripen—and eventually rot.

Additionally, an apple that is infested with mold will contaminate other fruit it's stored with as the mold seeks additional food sources and spreads.